The present invention relates to microcomputers having a motor controller circuit for controlling a three-phase inverter motor.
A conventional three-phase inverter motor controlling circuit is shown in FIG. 4. A microcomputer 1 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a timer, and an oscillator for generating clock pulses, all of which are provided on a single chip. A gate array or additional circuit 2 converts the waveforms of pulse width modulation signals outputted from the microcomputer 1 into inverter output waveforms.
As shown in FIG. 5, the microcomputer 1 and the additional circuit 2 are mounted on a printed circuit board 3 to form a motor controller unit.
In operation, the PWM signals from the microcomputer 1 are converted by the additional circuit 2 into three-phase inverter waveforms or motor drive signals in phases U-W for controlling the motor. This conventional circuit, however, requires a gate array and an additional circuit which uses many components. The motor controlling unit shown in FIG. 5 requires a large mounting area, and is sensitive to noise and high in the unit manufacturing cost.